A typical cable is constructed of metal conductors insulated with a polymeric material. These insulated conductors are generally twisted to form a core and are protected by another polymeric sheath or jacket material. In certain cases, added protection is afforded by inserting a wrap between the core and the sheath. A typical fiber optics cable can be made up of one or more glass fibers.
A particular cable useful in shipboard and other vehicular applications is referred to as a tray cable. The "tray" is simply a support for one or usually several cables. It is used in cases where the cable(s) cannot be elevated as on poles or towers or buried in the ground. The tray can be in the form of a conduit having, for example, a cylindrical or box-like shape, and containing a one or more cables.
In order to pass certain vertical flame tests such as Institute of Electrical and Electronics Engineers (IEEE) Standard 383 and Underwriters Laboratories (UL)-1685, the insulation or jacketing compositions for tray cables, which are typically non-halogen, flame retardant crosslinked compositions, are usually formulated with at least 55 percent by weight of hydrated inorganic fillers (also referred to as hydrated mineral fillers or metal hydrates). At such a high filler loading level, these compositions are extremely viscous, which detracts from various of their properties, most notably flexibility, tear strength, and their resistance to hydrocarbon and other machine fluids used on ships and other vehicles such as lubricants, hydraulic fluids, turbine fuels, and diesel fuels.
Silanes are often used as coupling agents between fillers and polymeric material to enhance property performance at a sacrifice in tear strength, and ethylene/vinyl acetate (EVA) copolymers are typically used as the polymeric material in flame retardant compositions due to their high filler acceptability and flexibility, but are also deficient in tear strength. In addition, the EVA copolymers have poor fluid resistance. In sum, the EVA copolymer/silane coupling agent/hydrated mineral filler combination is found to provide high filler acceptability and flexibility, but relatively low fluid resistance and tear strength. It is further found that the more hydrated filler present in this combination, the better the flame retardancy, which would be expected; however, there is a corresponding decline in processability.